cgroups: net_cls as module

Allows the net_cls cgroup subsystem to be compiled as a module

This patch modifies net/sched/cls_cgroup.c to allow the net_cls subsystem
to be optionally compiled as a module instead of builtin.  The
cgroup_subsys struct is moved around a bit to allow the subsys_id to be
either declared as a compile-time constant by the cgroup_subsys.h include
in cgroup.h, or, if it's a module, initialized within the struct by
cgroup_load_subsys.

Signed-off-by: Ben Blum <bblum@andrew.cmu.edu>
Acked-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Paul Menage <menage@google.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 1 deletions

diff --git a/net/sched/Kconfig b/net/sched/Kconfig
index 21f9c7678aa3..2f691fb180d1 100644
--- a/net/sched/Kconfig
+++ b/net/sched/Kconfig
@@ -328,13 +328,16 @@ config NET_CLS_FLOW
           module will be called cls_flow.
 
 config NET_CLS_CGROUP
-        bool "Control Group Classifier"
+        tristate "Control Group Classifier"
         select NET_CLS
         depends on CGROUPS
         ---help---
           Say Y here if you want to classify packets based on the control
           cgroup of their process.
 
+          To compile this code as a module, choose M here: the
+          module will be called cls_cgroup.
+
 config NET_EMATCH
         bool "Extended Matches"
         select NET_CLS